| Manning Construction (Northampton) Limited | Construction | 2010 |
| Manning Court Management Limited | Households | 1999 |
| Mannion Consulting Limited | Information & communication | 2018 |
| Mannsupply Limited | Administrative & support | 2025 |
| Mannys Property Group Limited | Real estate | 2026 |
| Manole.Man Ltd | Transport & logistics | 2022 |
| Manor Air Products Limited | Construction | 2023 |
| Manor Alliance Group Ltd | Financial services | 2019 |
| Manor Farm Ravensthorpe Limited | Professional & scientific | 2012 |
| Manor Farm RTM Company Limited | Households | 2025 |
| Manor Farm Wools Limited | Wholesale & retail | 2024 |
| Manor Gardens (Hanging Houghton) Management Co Ltd | Other services | 2009 |
| Manor Global Machinery Ltd | Wholesale & retail | 1991 |
| Manor Heath Residents Management Company Limited | Real estate | 2021 |
| Manor Landscapes (Midlands) Limited | Administrative & support | 2015 |
| Manor Office Furniture Ltd | Manufacturing | 2020 |
| Manor Road Grendon Management Company Limited | Households | 2006 |
| Manor Stays Ltd | Hospitality | 2019 |
| Manor UK Services Limited | Professional & scientific | 2021 |
| Manormax Ltd | Hospitality | 2023 |
| Manouver Driving Ltd | Education | 2024 |
| Mansfield Board Machinery Limited | Professional & scientific | 1978 |
| Mansfield Practice Limited | Health & social care | 2010 |
| Mansfield Sports Group Limited | Manufacturing | 2013 |
| Manson's (Hotels) Limited | Real estate | 1965 |
| Manta Recruitment Ltd | Administrative & support | 2016 |
| Mantenatal Ltd | Education | 2022 |
| Mantic Design Limited | Information & communication | 2020 |
| Manton Engineering (Bedford) Limited | Manufacturing | 1976 |
| Mantra Scaffolding Services Ltd | Construction | 2024 |
| Mantse Agbo Ventures Limited | Information & communication | 2025 |
| Manuals Sewing Services Limited | Manufacturing | 2002 |
| Manuel Rose Services Ltd | Administrative & support | 2024 |
| Manufacturing Print Technologies Limited | Extraterritorial | 1995 |
| Manzil Ecom Ltd | Wholesale & retail | 2026 |
| Maple Business Consulting Limited | Professional & scientific | 2002 |
| Maple Hollow Estates Limited | Construction | 2005 |
| Maple Mountain View Limited | Other services | 2023 |
| Maple Tree Service and Landscaping Limited | Construction | 2017 |
| Maplyn Care Services Ltd | Health & social care | 2008 |
| Mapped OUT Investments Ltd | Financial services | 2023 |
| MAR Brickwork Ltd | Construction | 2022 |
| Maradu Transport Ltd | Transport & logistics | 2025 |
| Maral Jewelers Limited | Manufacturing | 2023 |
| Maramjess Limited | Information & communication | 2020 |
| Marbell Group Limited | Real estate | 2020 |
| Marcam Management Ltd | Real estate | 2019 |
| Marcel General Building Services Ltd | Construction | 2026 |
| Marcel Mortgage Solutions Ltd | Professional & scientific | 2016 |
| March Yard Ltd | Agriculture & fishing | 2012 |
| Marcham Limited | Financial services | 2021 |
| Marchant Associates Limited | Professional & scientific | 2020 |
| Marchesi Ltd | Professional & scientific | 2012 |
| Marchway Properties Limited | Real estate | 2005 |
| Marcin Gorowski Transport Ltd | Transport & logistics | 2025 |
| Marcin Maciaszek Ltd | Administrative & support | 2021 |
| Marcle Business Solutions Limited | Professional & scientific | 2004 |
| Marco PL Ltd | Transport & logistics | 2017 |
| Marcopolo Euro Market Ltd | Wholesale & retail | 2024 |
| Marcross Building Services Limited | Construction | 2002 |
| Marctob Services Limited | Other services | 2019 |
| Marcus Publishing Public Limited Company | | 1984 |
| Marcus Rock Engineering Ltd | Professional & scientific | 2017 |
| Marefair Healthcare Limited | Health & social care | 2025 |
| Marefair Limited | Real estate | 2018 |
| Marekmd Ltd | Transport & logistics | 2026 |
| Marela Properties Limited | Real estate | 2001 |
| Margaret Bates Consultancy Ltd | Professional & scientific | 2026 |
| Margherita HUT Ltd | Hospitality | 2018 |
| Marguni Courier Ltd | Transport & logistics | 2022 |
| Marhall Holdings Limited | Health & social care | 2009 |
| Mari Miko Ltd | Other services | 2024 |
| Maria Costello Motorsport Limited | Professional & scientific | 2006 |
| Maria I Trans Limited | Administrative & support | 2017 |
| Maria Peralta Architects Ltd | Professional & scientific | 2026 |
| Maria Trans Ltd | Transport & logistics | 2020 |
| Marian & Fiber Optic Ltd | Construction | 2023 |
| Marian Construc Limited | Education | 2025 |
| Marian Iliescu Spedition Limited | Other services | 2019 |
| Marian Lupu Limited | Transport & logistics | 2020 |
| Marias Flower Parlour Limited | Wholesale & retail | 2026 |
| Marie Trade Commodities Enterprise Limited | Wholesale & retail | 2023 |
| Marie Trade Enterprise Ltd | Wholesale & retail | 2019 |
| Marigen Products Limited | Wholesale & retail | 2010 |
| Marigen Services Limited | Other services | 2025 |
| Marigold Cosmetics Ltd | Wholesale & retail | 2017 |
| Marimatt Limited | Financial services | 2025 |
| Marin Marinov Driving Services Limited | Transport & logistics | 2016 |
| Marincea Bricks Ltd | Construction | 2025 |
| Marine Division Limited | Manufacturing | 2020 |
| Marine Entertainment Technical Ltd | Administrative & support | 2024 |
| Marine Tech Service 1983 Ltd | Manufacturing | 2024 |
| Marines Transport Limited | Transport & logistics | 2021 |
| Mario Developments Ltd | Construction | 2018 |
| Mario Express Ltd | Transport & logistics | 2026 |
| Mario Luca Ltd | Transport & logistics | 2022 |
| Mario Peto Transport Ltd | Transport & logistics | 2025 |
| Mario Security Ltd | Administrative & support | 2020 |
| Mario Transport & Logistics UK Ltd | Transport & logistics | 2019 |
| Marios Ice Cream Ltd | Hospitality | 2021 |